Transmission power control, TPC, transmitting single or multiple TPC bits from a radio base station, RBS, to a mobile station, MS, or vice versa informing the receiving party to increase or decrease the transmission power level, optionally by a specified amount, is previously known.
Transmission power control compensates for signal fading and interference dynamics at a receiver. Closed loop power control according to prior art is described in relation to FIG. 1. In closed loop power control received pilot channel signal to interference ratio, SIR, is measured at the receiving end (RBS for uplink). The level of the SIR equals the SIR or a quantized value thereof. The level of the SIR is compared with a target level. Information on the outcome of the comparison is fed back in the reverse direction in the form of TPC commands. Radio wave propagation and power control processing introduces a delay in the feedback loop. To achieve a feedback loop with minimum (one slot) delay, transmission power response and measurement should be controlled within one slot. The transmitting end adjusts transmission power in response to received TPC commands. The receiving end receives, at a propagation delayed time, a pilot signal transmitted at the adjusted level, closing the power control loop. If the level of the measured SIR is larger than the target level, the receiving end transmits a command towards the transmitting end (MS for uplink) to decrease the power at the transmitting end. If the level of the measured SIR is smaller than the target level the transmitting end is correspondingly instructed to increase the transmission power. Finally, if the level of the measured SIR is equal to the target level the receiving end receives no command, a command of no change of transmission power or interchanging commands of transmission power increase and decrease to keep the transmission power close to constant. The command to increase or decrease transmission power is sent by means of one or more TPC bits. A TPC command determined accordingly and within a predetermined one slot loop delay, irrespective of whether it refers to uplink or downlink power control, is called a regular TPC command in this patent application.
In FIG. 1, an optional, dependent on slot format and link direction, TFCI field represents a Transport Format Combination Indicator for use e.g. when several simultaneous services are included.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical Layer Procedures, 3G TS 25.214 v3.3.0, France, June 2000, specifies in annex B.1 that timing of an uplink dedicated physical channel, DPCH, is delayed by 1024 chips from the corresponding downlink DPCH to maximize cell radius within which one-slot control delay can be achieved. In the sequel this maximum radius is referred to as the one-slot distance to the base station. Basically, a TPC command comprises one bit, indicating a power increase or decrease. During soft handover there is one such basic TPC bit or TPC command for each of the links involved, to be combined into a TPC command. Consequently, the concept “TPC command” comprises both such basic and combined TPC commands. The 3GPP Technical Specification also describes out of synchronization handling. Briefly, poor quality link sets are indicated to be out of sync. Regarding uplink power control, the MS shall shut its transmitter off during downlink out-of-sync conditions. If the receive timing for any link, during soft handover, drifts to lie outside a valid range, information shall be provided, so that the network can adjust downlink timing. Regarding downlink power control, during out-of-sync periods the TPC command transmitted shall be set as “1”, i.e. it shall indicate a power increase.
European Patent Application EP0955735 discloses a method, and base and mobile stations for locating transmission power control data and pilot data in relation to each other within a slot taking into account processing delays and propagation delays and slot offsetting between uplink and downlink.
None of the cited documents above discloses a closed loop transmission power control, TPC, with the location of TPC data within a slot fixed for two or more slots in relation to pilot symbols, the power control being adaptive to loop delays varying to be larger than or smaller than the duration of one slot.